His wife, Kwa Geok Choo, died last year, and Mr. Lee has taken pains recently to focus Singaporeans on challenges he says they may face once he isn't around, including the potential for complacency among younger citizens who don't fully appreciate the work that went into building the city-state in previous decades.

Died: Kwa Geok Choo, the wife of Singapore's founding father, Lee Kuan Yew, who described her as his "tower of strength," and mother of the city-state's current prime minister, in Singapore on Saturday at age 89.